What the symbols mean
The neutrino symbols (e.g. n) represent a type of neutrino; it may be a muon or a tau neutrino, or it may be some mixture of the two which is given a numerical label.
To keep these types of calculations as uncluttered, physicists avoid writing frequently occuring constants like, say, the speed of light ("c"). So for instance, Einstein's famous equation E = mc2 can also just be written E = m, if you measure E and m in appropriately chosen units.